An Aliphatic Solvent-Soluble Lithium Salt of the Perhalogenated
Weakly Coordinating Anion [Al(OC(CCl<sub>3</sub>)(CF<sub>3</sub>)<sub>2</sub>)<sub>4</sub>]<sup>−</sup>
- Publication date
- Publisher
Abstract
The
facile synthesis of a new highly aliphatic solvent-soluble Li<sup>+</sup> salt of the perhalogenated weakly coordinating anion [Al(OC(CCl<sub>3</sub>)(CF<sub>3</sub>)<sub>2</sub>)<sub>4</sub>]<sup>−</sup> and its application in stabilizing the Ph<sub>3</sub>C<sup>+</sup> cation were investigated. The lithium salt Li[Al(OC(CCl<sub>3</sub>)(CF<sub>3</sub>)<sub>2</sub>)<sub>4</sub>] (<b>4</b>) was
prepared by the treatment of 4 mol equiv of HOC(CCl<sub>3</sub>)(CF<sub>3</sub>)<sub>2</sub> with purified LiAlH<sub>4</sub> in <i>n</i>-hexane from −20 °C to room temperature. Compound <b>4</b> is highly soluble in both polar and nonpolar solvents, and
it bears both CCl<sub>3</sub> and CF<sub>3</sub> groups, resulting
in a lower symmetry around the Al center compared to that of Li[Al(OC(CF<sub>3</sub>)<sub>3</sub>)<sub>4</sub>] (<b>1</b>). Treatment of <b>4</b> with Ph<sub>3</sub>CCl afforded the ionic compound [Ph<sub>3</sub>C][Al(OC(CCl<sub>3</sub>)(CF<sub>3</sub>)<sub>2</sub>)<sub>4</sub>] (<b>5</b>) bearing the Ph<sub>3</sub>C<sup>+</sup> cation with concomitant elimination of LiCl, suggesting the potential
application of [Al(OC(CCl<sub>3</sub>)(CF<sub>3</sub>)<sub>2</sub>)<sub>4</sub>]<sup>−</sup> in stabilizing reactive cationic
species. Compounds <b>4</b> and <b>5</b> were fully characterized
by spectroscopic and structural methods
